1. Field of the Invention
The present invention relates to a method for manufacturing a header pipe of a heat exchanger for use as an evaporator or a condenser for an air conditioner, a radiator or heater core for a vehicle, or other type heat exchanger.
2. Description of the Prior Art
A typical conventional method for manufacturing a header pipe of such a heat exchanger is disclosed in JP-A-SHO 61-235698. In this conventional method, a planar raw plate for a header pipe is first bent into a cylindrical shape. The terminal ends of the opening side portions of the cylindrical raw plate are then brazed to each other. Thereafter, connection holes to which heat exchanger tubes are to be connected are opened on the surface of the cylindrical raw plate by punching.
However, since a pressing force due to a punching in such a conventional method is applied to portions other than the hole portion to be opened when the cylindrical raw plate is processed for punching the connection holes, a deformation is liable to occur on the header pipe. If such a deformation occurs, correction of the deformation is required, and the number of the processes for manufacturing the header pipe are thereby increased.
To solve this problem, the following manufacturing method has been proposed. Namely, connection holes for the heat exchanger tubes are first opened on a planar raw plate by punching. Thereafter, the punched raw plate is bent into a cylindrical shape. According to this method, the deformation of the header pipe can be prevented because the deformation caused by punching can be corrected when the punched raw plate is bent.
However, the heat exchanger tubes are inserted into the connection holes formed on the curved surface of the header pipe. In this manufacturing method, the size and shape of the connection holes opened on the planar raw plate must be determined by considering the size and shape of the connection holes which will be formed after the planar raw plate is bent. Therefore a high-accuracy processing is required for the punching. Moreover, even if the punching for the connection holes is performed with high accuracy, distortion of the connection holes is likely to occur in the successive bending process. Accordingly, it is difficult to make a header pipe with desired connection holes by this method.
In addition, a heat exchanger whose header pipe has therein at least one partition for turning a heat medium in the header pipe is also known. A typical conventional method for manufacturing such a header pipe is disclosed in Japanese Utility Model Laid-Open SHO 63-49193 as shown in FIG. 30.
In this conventional method, a hole 105 for receiving a partition plate 104, as well as connection holes 103 for heat exchanger tubes 102, are opened on a preformed cylindrical raw material 101 for defining a header pipe. Thereafter, heat exchanger tubes 102 are inserted into connection holes 103 and partition plate 104 is inserted into hole 105 from outside. The partition plate 104 is fixed in place temporarily. After the temporary fixing, partition plate 104 is formally fixed to cylindrical raw material 101 for a header pipe by brazing.
Thus, in the conventional method for manufacturing a header pipe with a partition, the processing for opening hole 105 for the insertion of partition plate 104 thereinto is necessary. Moreover, hole 105 must be formed of a size capable of receiving an inserting portion 106 of partition plate 104 into the hole 105. Namely, hole 105 is required to be of a size encompassing almost half of the circumference of cylindrical raw material 101. Therefore, brazing defects are likely to occur along hole 105 after insertion of the partition plate 104, which may cause leakage of a heat medium. Furthermore, since such a large hole 105 is formed in the wall of cylindrical raw material 101 for a header pipe, the strength of the header pipe is greatly decreased. Therefore, there is a fear that the cylindrical raw material 101 may be deformed when hole 105 is opened or when connection holes 103 are processed.